Avril Lavigne has stunned fans by announcing her engagement to Nickelback rocker Chad Kroeger.The Sk8er Boi hitmaker fell in love with the frontman after they teamed up to write a song for her new album in February (12), but they have managed to keep the romance out of the public domain. Lavigne's representative has now confirmed the singer recently accepted Kroeger's proposal. The news was first posted on Nickelback's official Twitter.com page, before Lavigne re-tweeted the message. She was previously married to Sum 41 frontman Deryck Whibley until they split in 2009. She also dated reality TV star Brody Jenner but they split earlier this year (12).